Ivor John Carnegie Brown CBE (25 April 1891 – 22 April 1974) was a British journalist and man of letters.

After graduating from Oxford with top honours, he joined the civil service, but left after two days to pursue a freelance career as a writer. He later joined the staff of The Manchester Guardian as its London drama critic, and subsequently wrote for, and for six years edited, The Observer. He was widely regarded as the leading drama critic of his generation.

Brown was a prolific author; he published more than seventy-five books – some of them compilations of his journalism, and others about words, their origins, meaning and use.

Brown was born in Penang, Malaya, on 25 April 1891, the younger of two sons of William Carnegie Brown, a specialist in tropical diseases, and his wife Jean, née Carnegie. His father had a practice in Malaya, and Brown was sent to England to be educated at Suffolk Hall preparatory school and then, from 1902 to 1907, at Cheltenham College. He then undertook a year's private tuition with a crammer after which he headed the scholarship list at Balliol College, Oxford, where he shared the Jenkyns exhibition in 1913 and took a double first in classical honour moderations (1911) and literae humaniores (1913).

In the entrance examination for the civil service in 1913 he came sixth out of eighty-four successful candidates. Those above him went on to distinguished careers as public servants, but Brown did not. He was assigned to the Home Office, where his career lasted two days: finding himself asked to deal with an application by Staffordshire police for the increased provision of lavatories he wrote his comments and walked out, to earn his living writing as a freelance about subjects of more interest to him. He became involved in progressive politics, and was a conscientious objector during the First World War. He lectured for the Oxford Tutorial Classes Committee, published three novels and two other books: English Political Theory and The Meaning of Democracy and wrote articles for The New Age, an "independent socialist review of politics, literature and art". The Times later described his articles as "trenchant and witty".

On 4 January 1916 Brown married Irene Gladys Hentschel (1890–1979), an actress and later a director. The biographer Philip Howard writes, "her knowledge of the far side of the footlights enriched her husband's criticism". The marriage was lifelong. They had no children.

In 1919 Brown joined the staff of The Manchester Guardian at its London office, as a leader writer and the paper's London drama critic, serving from then until 1935. His opposite number on The Daily Telegraph, W. A. Darlington, wrote of Brown, "No contemporary drama critic has enjoyed a higher reputation for good judgment combined with witty and scholarly writing". J. C. Trewin called him the leading English drama critic of his time ... wise, balanced, modest and a master-stylist [who] will stand with the few major English critics".

The Times commented that it fell to Brown to interpret "the great outburst of new and experimental modes of playwriting" that followed the war. His responses to the expressionists such as Karel Čapek, Luigi Pirandello, Elmer Rice and Eugene O'Neill were collected in a volume, Masques and Phrases (1926), compiled from his press reviews. The Times commented that it remains a valuable commentary on a remarkable chapter in the history of the theatre. Brown had his blind spots: as late as 1934 he dissented from the – by then – wide admiration led by F. R. Leavis, F. O. Matthiessen, Cleanth Brooks and others of T. S. Eliot and The Waste Land. He said that Eliot "offers the public the balderdash of his Waste-land (pretentious bungling with the English language?) and immediately becomes a pundit, bestriding the Atlantic". He was equally dismissive of Ezra Pound.